Small seed-eating bird of humid tropical lowlands; fairly common. Found in grassy and weedy areas and forest edges, often in same places as slightly larger Thick-billed Seed-Finch. In pairs or small flocks, mixing readily with White-collared Seedeaters and other seed-eating birds. Note stubby bill (unlike Thick-billed Seed-Finch) and plain brownish olive plumage of female (not rich brown like seed-finch). Males in Mexico and most of Central America are black. In southern Central America males have variable amounts of white on the underparts and rump, hence the name.